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Studying Cryptosporidium Infection in 3D Tissue-derived Human Organoid Culture Systems by Microinjection
Published on: September 14, 2019
Characterization of a single dose methylprednisolone acetate immune suppression model using Cryptosporidium muris and
Thomas A Miller1, Frank W Schaefer
1US Environmental Protection Agency, Cincinnati, OH 45268, USA.
Abstract:
An immunosuppressive dose of methylprednisolone acetate (MPA) was compared with a non-immunosuppressive dose using Cryptosporidium oocyst production as an indicator of immunosuppression. To be classified as immunosuppressive, the dose had to satisfy five criteria. First, the dose had to abrogate normal immune defenses allowing the propagation of an organism to which the host is normally resistant, i.e. Cryptosporidium parvum in adult mice. Second, the dose had to decrease overall circulating CD4 T-lymphocyte numbers by greater than 80%. Third, the immunosuppressive dose had to prolong the infection beyond the normal infection length, and fourth, increase the severity of an active infection. Lastly, after complete recovery from a C. muris infection, immunosuppression must suppress the naturally acquired post infection immunity and allow reinfection. In mice immunosuppression with 600 mgMPA/kg lasted approximately 14 days and satisfied all five criteria. Fecal oocyst production could be perpetuated by dosing at 10-day intervals. A 200 mgMPA/kg dose transiently lowered CD4 counts by over 80%, but failed to override the naturally acquired post infection immunity or allow infection with C. parvum. The immunosuppressed blood profile consisted of an immediate sharp rise of mature segmented neutrophils combined with a severe decrease in circulating T-lymphocyte numbers. The rise and fall of neutrophils proved to be a good indicator of the severity and duration of immunosuppression. The thymus and spleen likewise contracted and then expanded in accordance with the steroid effect. The metabolism of MPA resulted in the eventual recovery of immune function signified by the cessation of C. parvum oocyst production. The recovery blood profile was associated with circulating CD8 counts near control levels, continuing 80% depression of CD4 counts and a dropping total neutrophil count. This study shows that the 600 mg/kg MPA dose is a good model for immunosuppression, which satisfies all five criteria for immunosuppression with low morbidity and low mortality.
Insights
A high dose of methylprednisolone acetate (MPA) effectively models immunosuppression in mice by enabling parasite infection and altering immune cell counts. This immunosuppression model shows low morbidity and mortality, aiding immune function studies.
Area of Science:
- Immunology
- Pharmacology
- Infectious Disease
Background:
- Methylprednisolone acetate (MPA) is a corticosteroid with known immunosuppressive effects.
- Establishing reliable animal models for immunosuppression is crucial for studying immune responses and disease pathogenesis.
Purpose of the Study:
- To evaluate a high dose of MPA as an immunosuppressive model in mice using specific immunological and parasitological criteria.
- To compare the effects of an immunosuppressive MPA dose with a non-immunosuppressive dose on immune defenses against Cryptosporidium.
Main Methods:
- Adult mice were treated with either 600 mg/kg (immunosuppressive) or 200 mg/kg (non-immunosuppressive) of MPA.
- Immunosuppression was assessed based on five criteria: susceptibility to Cryptosporidium parvum, reduction in CD4 T-lymphocytes, infection duration, infection severity, and abrogation of post-infection immunity.
- Blood cell counts (neutrophils, T-lymphocytes), thymus and spleen size, and fecal oocyst production were monitored.
Main Results:
- The 600 mg/kg MPA dose met all five criteria for immunosuppression, lasting approximately 14 days and allowing Cryptosporidium propagation.
- A transient >80% decrease in CD4 T-lymphocytes was observed with the high MPA dose, accompanied by a rise in neutrophils.
- The 200 mg/kg MPA dose did not override natural immunity or permit Cryptosporidium infection.
- Recovery from immunosuppression was indicated by the cessation of oocyst production and normalization of neutrophil counts.
Conclusions:
- The 600 mg/kg MPA dose serves as a robust and valid model for studying immunosuppression in mice, fulfilling all established criteria with minimal morbidity and mortality.
- This model facilitates research into the dynamics of immune suppression and recovery, as well as host-parasite interactions.
